Coating of Metal Sheets and Strips, Energy Technologies

At Fraunhofer FEP, a pilot plant for coating bipolar plates for electrolyzers and fuel cells has been qualified. This technology is cost-effective and enables high productivity as a contribution to the success of the energy transition.

Highly productive and cost-effective production technologies are required to successfully ramp up the hydrogen economy. To this end, the in-line vacuum coating plant MAXI for plasma-activated electron beam evaporation using spotless arc-activated deposition (SAD) was qualified for the highly productive and efficient coating of bipolar plates for electrolyzes and fuel cells.

Bipolar plates have to perform with long-term stability in a chemically aggressive environment and require protective coatings such as titanium. At the same time, sufficient electrical conductivity must be ensured, for example by an additional carbon coating.

Using plasma-activated electron beam physical vapor deposition, for example, ductile, formable coatings can be applied to metal strip before it is stamped into bipolar plates. Coating the material prior to the embossing process is considered as a decisive step for upscaling production in the roll-to-roll process. One challenge for formability is to ensure a dense macrostructure.  

These layer properties can be realized by the processes such as SAD developed at Fraunhofer FEP, and with the plant MAXI, an innovative roll-to-roll as well as sheet-to-sheet line for the high-rate coating  of corresponding substrates is available for research and development as well as for pilot production. Initial results in the coating of 250 mm wide and 50 µm thick metallic strips with titanium already exhibited homogeneous layers in the thickness range of 100 nm with a dense structure, which could be produced at strip speeds of 10 m/min. The advantage of this process is that the substrate temperature can be limited to maximum values of less than 250°C. This means that the temperature can be kept to a minimum. Furthermore, due to the low heat load, sensitive materials such as electrically conductive polymers can be coated, which represent an innovative alternative for batteries and fuel cells.

The research activities were carried out in close cooperation with Fraunhofer IWU and VON ARDENNE GmbH.